The Yoga Tune Up Therapy Balls (also known as the "OG's") measure at about 2 1/2" in diameter each and are made of a special rubber that grips at your skin, grabs at multiple layers of muscles, and rubs out adhesion and tension, providing a deep tissue massage. The Yoga Tune Up® Therapy Balls with Tote set includes two foot massage balls and a mesh drawstring snug-grip tote bag. The ball that started it all!